A variety of assembly units, e.g., catalytic converters and particle filters, are used for exhaust gas treatment in exhaust systems of internal combustion engines used, for example, in motor vehicles. In order to protect such assembly units against environmental effects or to insulate them thermally, covering a housing of same, which is generally composed of sheet metal material, with a covering device on its outside is known. Such a covering device may comprise, for example, a fibrous insulating material, which is in contact with the outside of the housing, on the one hand, and is enclosed on its outwardly exposed surface by an additional sheet metal housing providing a layer of protective material, on the other hand.
To be able to collect information about the states present in such exhaust gas treatment devices, for example, to be able to detect the temperature in the interior of such an exhaust gas treatment device or to be able to provide information about the exhaust gas composition, it is known to provide at a housing of such a device one or more connection pieces, via which there is access to the interior of the housing and on each of which a measuring probe, e.g., a temperature sensor or an exhaust gas sensor, can be mounted. In the area, in which such a connection piece is fixed or is to be fixed to the housing of an exhaust gas treatment device, the covering device overlapping the housing must have an opening suitable for the passage of the connection piece through the covering device. In the area of such an opening there is generally a gap-like intermediate space between the connection piece and an edge area of the covering device, so that the housing of the exhaust gas treatment device is not overlapped outwardly by the covering device in this area.